Beamforming is a signal processing technique that can be used to improve reception quality and increase data throughput in a wireless communication network. In a wireless communication network employing beamforming, relative gain and phase of an array of antennas elements can be adjusted so that an antenna beam can be directed for receiving or transmitting data. Beamforming using directional antennas concentrates electromagnetic energy to produce a radiation pattern in one or more desired directions.
Due to lack of available low frequency bands, future radio systems are expected to be operated at high frequency bands. The disadvantage is that the propagation attenuation of high frequency is much larger than the low frequency. By way of example, the attenuation may be approximately proportional to the square of the carrier frequency in the same propagation environment. In order to ensure coverage, High Gain Beam Forming (HGBF) is being paid more and more attention. As beamforming gain is roughly proportional to the number of integrated antenna elements, significant beamforming gain can be expected with large number of antenna elements. With high gain beamforming, the spatial beam would be rather narrower compared to conventional systems.
Discontinuous Reception (DRX) is an important method for both power saving and signaling overhead reduction. In the DRX state, the terminal device wakes up for data reception in an active duration (also referred to as “wake period”) and goes to sleep for an inactive duration (also referred to as “sleep period”) in turn, and thus can keep radio connection at low power consumption. For the network, it saves the signaling overhead due to frequently paging and radio connection establishment and release for small data transmissions.
However, in the high gain beamforming, coverage of a beam is relatively small due to the narrow beam width. If the terminal device receives data over a beam in an active duration and moves fast in the following inactive duration, it is possible that the terminal device goes beyond the coverage of the beam and cannot receive data any more when it enters the next active duration. Thus, an undesirable beam mismatching issue which deteriorates transmission quality would occur and needs to be mitigated.